1. Field of the Invention
The present invention relates to an organic electroluminescent device and a method of manufacturing the same. More particularly, the present invention relates to an organic electroluminescent device including a porous oxide layer, with an extended life span due to an improvement in moisture and oxygen adsorption, and to a method of manufacturing the same.
2. Description of the Invention
Organic electroluminescent (EL) devices are self emission displays that emit light by recombination of electrons and holes in a thin layer made of a fluorescent or phosphorescent organic compound when current is applied to the thin layer. Organic EL devices have advantages such as lightweight, simple constitutional elements, ease of fabrication, superior image quality, and wide viewing angle. In addition, organic EL devices have electrical properties suitable for portable electronic equipment such as high quality dynamic images, high color purity, low power consumption, and low driving voltage.
However, organic EL devices are easily deteriorated by the entry of moisture. Therefore an encapsulation structure for preventing the entry of moisture is required.
Conventionally, a metal can or a glass substrate etched in the form of a cap with a groove is used for encapsulation. In such a case, for moisture adsorption, a desiccant of a powder type is mounted in the groove or a desiccant of a film type is adhered in the groove by means of a double-sided tape. However, the process of manufacturing with a powder-type desiccant is complicated, and material and process costs are high. In addition, the thickness of the substrate increases and substrates intended for encapsulation are not transparent, which renders front emission difficult. On the other hand, the film-type desiccant insufficiently prevents the entry of moisture and the desiccant may be easily broken during fabrication or use, thereby lowering durability and reliability, and rendering mass production difficult. In addition to the above problems, even though use of a metal can may ensure structural firmness, the etched glass is structural weak and may be easily damaged by external impact.
Japanese Patent Laid-Open Publication No. Hei. 9-148066 discusses an organic EL device including a laminate having a pair of electrodes opposite to each other and an organic light-emitting material layer made of an organic compound interposed between the electrodes, an airtight container for preventing exposure of the laminate to the air, and drying means made of, for example, alkaline metal oxide, disposed in the airtight container. However, the bulky shape of the airtight container increases the total thickness of the organic EL device. Also, opaqueness of the drying means renders the fabrication of a front emission type organic EL device difficult, even though the drying means is maintained in a solid state after adsorbing moisture. In addition, the fabrication process is complicated, increasing material and process costs.